On construction jobsites, there is a need for locating points of interest on two-dimensional horizontal surfaces. A simple, accurate and cost effective system for the layout of floor plans at the jobsite has long been in need. Conventional GPS is not usable inside standard steel construction buildings, and previous laser based systems have been overly complex and expensive.
Two earlier patent documents have advanced the art in this area in a significant way, disclosing a laser system that provides the elements for visually locating points of interest on a two-dimensional horizontal surface. A pair of “base units” are placed on the jobsite surface, and these base units have certain capabilities that are described in those earlier patent documents. One of these documents is U.S. Pat. No. 8,087,176; a second such document is published application number US 2012/0203502; both patent documents are commonly-assigned to Trimble Navigation Limited.
These patent documents teach using a vertical fan beam, consisting of (typically modulated) laser light that is emitted by a first base unit. The goal is to adjust the aim of the fan beam of the first base unit until its laser light line that travels along the jobsite surface (floor or ceiling) runs directly through a point of interest on that jobsite surface. Once that has occurred, the second base unit is adjusted so that its vertical fan beam is aimed so that its laser light line that travels along the jobsite (floor or ceiling) surface runs directly through the same point of interest on that jobsite surface. After both base units have been correctly aimed, angular positions (in the azimuth direction, for example) can be determined and recorded, as desired.
In bright-lighting conditions, or in situations where the point of interest is physically a long distance from the base unit, the fan beam-produced laser light lines might be relatively difficult to see on the desired (floor or ceiling) jobsite surface. It would be beneficial to have some type of reflective laser light target to highlight the position where the two laser fan beams intersect on that jobsite surface.